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Stellar Shock Wave

StarDate:

January 5, 2011

The relationship between stars and the material around them -- the interstellar medium -- is complicated. Stars are born from this material -- wispy clouds of hydrogen, helium, and other elements, plus solid grains of dust. And when stars die, they expel much of their material back into the interstellar medium, enriching it with elements forged in the hearts of the stars themselves.

And between birth and death, a star can have a powerful influence on the interstellar medium around it.

An example is the star known as Alpha Camelopardalis. It's one of the brightest stars of the faint constellation Camelopardalis, the giraffe, which is high in the north on January evenings.

Alpha Cam is probably 25 to 30 times as massive as the Sun. That great heft makes its surface extremely hot, driving a strong "wind" of gas off the surface and into space, forming a big "bubble" around Alpha Cam.

The star is racing through space at more than a hundred thousand miles an hour. As it plows through the interstellar medium, its wind squeezes the cooler gas and dust ahead of the star, forming a bow shock -- like water piling up in front of a ship. The shock wave spans several light-years.

Over time, it's possible that the shock wave could help compress the interstellar medium enough to give birth to new stars -- continuing the complex relationship between the stars and the material around them.

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